1. Field of the Invention
This invention relates to drum brakes, and more specifically to an improved drum brake hydraulic cylinder device. The preferred embodiment of the disclosed invention is a brake cylinder made of a corrosion resistant metal, such as stainless steel, with an O-ring in an annular groove in the cylinder chamber. One specifically disclosed embodiment shows a brake cylinder with an additional exterior seal. Another specifically disclosed embodiment is universal to either left side drum brakes or right side drum brakes.
2. Discussion of Prior Art
Drum brake hydraulic brake cylinders are well-known in the prior art. These devices are used to spread the brake shoes, pressing them against the brake drum to slow the vehicle. In typical prior art devices, as shown in FIG. 1, the cylinder body (10) is made of steel, and the piston (18) is made of aluminum. Under pedal pressure, hydraulic fluid (not shown) enters through an inlet passage (12) into the cylinder chamber (34) and presses against a rubber cup seal (22) which drives the piston (18) out, spreading the brake shoes (not shown). To bleed the brakes, each cylinder has a bleeder valve (not shown) which must be at the top of the cylinder, the location of unwanted air. The bleeder valve is threaded into a bleeder valve passage (14) in the cylinder. Typical prior art devices are manufactured in left side and right side versions to locate the bleeder valve at the top of the cylinder.
Problems arise when these devices are immersed in salt water and fresh water, as is common with boat trailers. The cup seal does not seal the piston or the cylinder from water, and the piston may seize in the cylinder due to rust and corrosion.
Costs associated with left side and right side versions of brake cylinders are high. Separate left side and right side components must be designed, manufactured, and stocked. Mechanics must order and install the proper version.